The present invention relates generally to filter arrangements and, more specifically, to a filter arrangement for shaping a pulse or signal propagated over POTS wiring to implement a networked computer environment.
Nodes comprising a data network may transmit and receive information over a guided media, such as metal wire or fiber-optic cable, or an unguided media, such as by infrared or microwave. Copper cable is a relatively inexpensive, well-understood technology that is easily installed and is accordingly the cable of choice in a majority of network installations. However, copper cable suffers from various electrical characteristics that impose transmission limits. Types of copper cable that may be used to transmit digital signals comprise straight cable (i.e., copper wire surrounded by an insulated sheath), twisted-pair cable (i.e., a pair of copper wires that are twisted together to former pair) and coaxial cable (i.e., a solid copper core surrounded by insulator, a combination shield and ground wire, and an outer protective jacket).
A recent and emerging method of implementing a network within a home, office or multi-dwelling unit proposes utilizing existing and installed telephone cable within the structure as the medium via which nodes may transmit and receive information. Such telephone cable (a.k.a. Plain Old Telephone Service (POTS) wiring) is often Category 1 or Category 2 Unshielded Twisted-Pair (UTP) telephone cable, and may accordingly be particularly susceptible to background noise. Specifically, such cable is specifically susceptible to background noise generated by external sources, such as adjacent lines, dimmer switches, AC and DC motors and modems.
The utilization of POTS wiring as a communication medium within a network environment presents number of challenges. Specifically, the presence of ringing on the POTS wiring resulting from the assertion of a pulse on the wiring may have negative implications for the reliability and operability of a network implemented over POTS wiring.
According to a first aspect of the present invention, there is provided a filter arrangement for shaping a signal transmitted over POTS wiring. The filter includes an input to receive the signal, a high-pass filter, and a low-pass filter coupled to the high-pass filter. A trap filter is coupled to both the high-pass and low-pass filters, the trap filter operationally introducing a filter zero at a resonant frequency of the high-pass filter. An output couples the filter arrangement to the POTS wiring.
According to a second aspect of the present invention, there is provided a method of constructing a filter arrangement for shaping a pulse transmitted of the POTS wiring. A low-pass filter is coupled to a high-pass filter. A trap filter is then coupled to both the high-pass and low-pass filters, the trap filter operationally introducing a filter zero at a resonant frequency of the high-pass filter.
According to a third aspect of the present invention, there is provided a Network Interface Card (NIC), adapter or line card including a filter arrangement as described above.